This invention relates to nondispersive infrared gas analyzers, and more particularly, to a nondispersive infrared gas analyzer of the type having a temperature radiator operated by a pulsed energy supply; the analyzer having gas-filled chambers arranged in the path of the modulated infrared radiation and a measuring pickup for producing an electrical measurement signal.
The principles and modes of operation of nondispersive infrared gas analyzers are well known. Modulation of the infrared radiation, which enhances the measurement effect, is frequently achieved by means of an aperture wheel which is rotated by an electric motor and which periodically interrupts the radiation. Although this arrangement achieves a desired 100% modulation, a relatively large amount of continuous energy is required for the temperature radiator to maintain it continuously at the operating temperature. In addition, the electrical motor which operates the aperture wheel also requires substantial continuous energy. Such substantial energy drains are particularly disadvantageous in battery operated equipment which is used in field investigations. In addition, equipment which is used in the field is subjected to mechanical shock and vibration, and must be operated in different positions, thereby adversely affecting the reliability of the mechanically operated parts.
In one known nondispersive infrared gas analyzer which is described in U.S. Pat. No. 3,105,147, some of the above-mentioned disadvantages are overcome by the use of an infrared radiation source which is modulated by a pulsed power supply. However, in order to achieve the desired 100% of modulation, the known pulsed radiators must be operated at very low pulse frequencies, thereby substantially reducing the sensitivity of the measuring device. Such a reduction in sensitivity is particularly acute in equipment which utilizes selective pneumatic receivers.
It is, therefore, an object of this invention to provide an improved nondispersive infrared gas analyzer which is useful as field equipment which operates without the need for a line power supply.
It is a further object of this invention to provide a nondispersive infrared gas analyzer wherein a high degree of modulation is achieved having undiminished sensitivity and low power comsumption.